An environmental control system, which is commonly referred to as an ECS, provides air supply, thermal control and cabin pressurization within an aircraft. Air is typically supplied to conventional ECS systems by bleed air extracted from a high pressure compressor of an aircraft engine. Specifically, the bleed air is usually extracted from a discharge or a low stage of the high pressure compressor of the aircraft engine. The bleed air is compressed or pressurized and heated to a relatively high temperature when compared to ambient conditions. Accordingly, the bleed air often needs to be cooled by a heat exchanger, which is also referred to as a pre-cooler, before being delivered to an ECS. The bleed air is cooled to a desired temperature and is then delivered to the ECS system. However, a substantial amount of energy may be spent by the aircraft engine in order to compress and cool the bleed air. Therefore, extracting bleed air from the aircraft engine may significantly reduce the engine's propulsive efficiency, which also results in an increase in the aircraft engine's Specific Fuel Consumption (SFC).
In one approach to reduce the amount of bleed air extracted from the aircraft engine, a compressor that receives ambient air from an atmospheric inlet may be provided. The compressor pressurizes the ambient air prior to being delivered to the ECS. However, this approach also has drawbacks, as the atmospheric inlet creates drag. Moreover, the atmospheric inlet may be susceptible to icing. Accordingly, the aircraft may be provided with an anti-icing system. However, the anti-icing system increases cost and system complexity of the aircraft.